The LeapFrog Leapster is great! Purchased it for my 4 yr. old for his birthday in May and didn't really play with it too much at first. But once he started pre-school, he plays with it all the time now (especially when we're driving long distances). The games have different learning levels, so they can advance to the next level at their own pace. It's been a FUN learning tool for my son. It's really helped with his recognition of letters/numbers without him realizing that he's learning. To him, it's just a game. He's already asked Santa for the SpongeBob Leapster game.
Another nice thing about the Leapster is the optional travle case, which holds and additional 3 cartridges. Small & compact...nice when you've got multiple kids to travel with. So we pack up the case & we're set for the road. (They've also come out with a messenger style backpack to store/carry the actual Leapster & all your game cartridges).
The inidvidual games can be expensive - ranges from $15 on sale to $24.99. But if the child's just starting out, a game or two is sufficient. I thought of the Leapster purchase as an investment. Suggestion is to keep an eye out for sales - example Toys R Us just had the games on sale for $19 the few weeks leading up to Black Friday. I have even seen the games on sale at Walmart.com for $15 with $.97 shipping. To me, that's a deal.
Happy toy hunting! And I'm sure you'll grandson will love whatever game he receives.
Happy Holidays!